Only once in the last of the part of the paper considered does Adami mention internal secretions. His actual words are: 'We recognise yearly more and more the existence of auto-intoxications, of disturbed states of the constitution due to disturbances in glandular activity or to excess of certain internal secretions or of the substances ordinarily neutralised by the same.' The only example he gives is that of gout. How remote this is from the discoveries concerning the specific action of hormones on the growth of the body or of special parts of the body, or on the function of glands, and from a definite hormone theory of heredity as proposed by myself, is sufficiently obvious. CHAPTER I Classification And Adaptation The study of the animals and plants now living on the earth naturally divides itself into two branches, the one being concerned with their structure and classification, the other with their living activities, their habits, life histories, and reproduction. Both branches are usually included under the terms Natural History, or Zoology, or Botany, and a work on any group of animals usually attempts to describe their structure, their classification, and their habits. But these two branches of biological science are obviously distinct in their methods and aims, and each has its own specialists. The pursuit, whose ultimate object is to distinguish the various kinds of organisms and show their true and not merely apparent relations to one another in structure and descent, requires large collections of specimens for comparison and reference: it can be carried on more successfully in the museum than among the animals or plants in their natural surroundings. This study, which may be called Taxonomics, deals, in fact, with organisms as dead specimens, and it emphasises especially the distinguishing characters of the ultimate subdivisions of the various tribes of animals and plants--namely, species and varieties. The investigation, on the other hand, of the different modes of life of animals or plants is based on a different mental conception of them: it regards them primarily as living active organisms, not as dead and preserved specimens, and it can only be carried on successfully by observing them in their natural conditions, in the wide spaces of nature, under the open sky. The object of this kind of inquiry is to ascertain what are the uses of organs or structures, what they are for, as we say in colloquial language, to discover what are their functions and how these functions are useful or necessary to the life of the animals or plants to which they belong. For example, some Cuttle-fishes or Cephalopoda have eight arms or tentacles and others ten. The taxonomist notices the fact and distinguishes the two groups of Octopoda and Decapoda.